156 UNSOLVED PROBLEMS. 



scarcely be said to be an explanation at all or always is that 

 certain singular attachments or companionships are deter- 

 mined by caprice. That such attachments, however, are of 

 the most various kind, differing probably in their nature or 

 causation, is shown by the following examples of them : 



1. The sudden attachments of dogs to human strangers, 

 whom they had never before seen, and of whom they conse- 

 quently knew nothing. 



2. The association of the pilot fish and shark ; or of the 



3. Sucking fish and the other larger fishes to which it 

 fastens itself ; or of the 



4. Zigzag (bird) and the crocodile. 



5. Of certain fishes and hermit crabs with certain sea 

 anemones. 



6. Of certain ants and blind beetles. 



7. Of certain pea crabs with mussels. 



8. Of the fishing frog and a kind of eel. 



Equally difficult of explanation are the remarkable anti- 

 pathies or aversions so frequently shown by dogs to certain 

 persons or things. There are many cases in which dislike, 

 more or less decided and permanent, is accounted for on 

 the ground of previous cruelty by a given person, and it is 

 quite possible that certain other cases are to be explained by 

 cruelty inflicted^on some progenitor, in which case dislike 

 to a particular class of men may become hereditarily trans- 

 mitted. But, even accepting such an explanation, it remains 

 to be determined how, by what means, dogs become aware 

 of the presence of a man belonging to a hereditarily hated 

 class. A few years ago much discussion took place in the 

 columns of ' Nature ' as to the hereditary hatred of butchers 

 by dogs. It was shown inter alia, by several well-known 

 authors that young dogs, that had never had any cause to 

 dislike fleshers or fleshers* shops, avoided, dreaded, or de- 

 tested both as thoroughly as older dogs that might themselves 

 have suffered from the cruelty of butchers when visiting 

 butchers' shops or otherwise, and that certain dogs could 

 detect a butcher even when well washed and dressed, far 

 away from his shop, and under circumstances that might 

 well have thrown the animals off their guard. In order to 



